8,101 research outputs found
Low energy ohmmeter can be used to test sensitive circuits, other meters
Hazardous circuit ohmmeter is of sufficiently low energy output that it may be used to test extremely sensitive circuits safely, reliably, and accurately. A polyurethane-foam-lined aluminum case provided protection for the unit assembly
Network Structure, Efficiency, and Performance in WikiProjects
The internet has enabled collaborations at a scale never before possible, but
the best practices for organizing such large collaborations are still not
clear. Wikipedia is a visible and successful example of such a collaboration
which might offer insight into what makes large-scale, decentralized
collaborations successful. We analyze the relationship between the structural
properties of WikiProject coeditor networks and the performance and efficiency
of those projects. We confirm the existence of an overall
performance-efficiency trade-off, while observing that some projects are higher
than others in both performance and efficiency, suggesting the existence
factors correlating positively with both. Namely, we find an association
between low-degree coeditor networks and both high performance and high
efficiency. We also confirm results seen in previous numerical and small-scale
lab studies: higher performance with less skewed node distributions, and higher
performance with shorter path lengths. We use agent-based models to explore
possible mechanisms for degree-dependent performance and efficiency. We present
a novel local-majority learning strategy designed to satisfy properties of
real-world collaborations. The local-majority strategy as well as a localized
conformity-based strategy both show degree-dependent performance and
efficiency, but in opposite directions, suggesting that these factors depend on
both network structure and learning strategy. Our results suggest possible
benefits to decentralized collaborations made of smaller, more tightly-knit
teams, and that these benefits may be modulated by the particular learning
strategies in use.Comment: 11 pages, 5 figures, to appear in ICWSM 201
Unconventional Fermi surface instabilities in the Kagome Hubbard Model
We investigate the competing Fermi surface instabilities in the Kagome
tight-binding model. Specifically, we consider onsite and short-range Hubbard
interactions in the vicinity of van Hove filling of the dispersive Kagome bands
where the Fermiology promotes the joint effect of enlarged density of states
and nesting. The sublattice interference mechanism [Kiesel and Thomale, Phys.
Rev. B Rapid Comm., in press.] allows us to explain the intricate interplay
between ferromagnetic fluctuations and other ordering tendencies. On the basis
of functional renormalization group used to obtain an adequate low-energy
theory description, we discover finite angular momentum spin and charge density
wave order, a two-fold degenerate d-wave Pomeranchuk instability, and f-wave
superconductivity away from van Hove filling. Together, this makes the Kagome
Hubbard model the prototypical scenario for several unconventional Fermi
surface instabilities.Comment: 4+e pages, 5 figure
Holographic and ultrasonic detection of bond flaws in aluminum panels reinforced with boron-epoxy
An experimental investigation was made of the application of holographic interferometry to the nondestructive detection of unbonded areas (flaws) in bonded panels. Flaw detection results were compared with results obtained with an ultrasonic flaw detector. Holography, with panel deformation accomplished by a reduction in ambient pressure, is less sensitive for flaws beneath 5 and 10 plies of boron-epoxy than the ultrasonic method, though it does have its operational advantages. A process for the manufacture of bonded panels which incorporate known unbonded areas was also developed. The unbonded areas were formed without the use of foreign materials, which makes the method suitable for the construction of reference standards for bonded panels whenever needed for the proper setup of ultrasonic flaw-detection instruments
Variation within and among species in a pine arboretum
The primary objective of this study was to obtain estimates of variation patterns in specific taxonomic and growth characteristics, within and among species of pines. Twenty-three species growing in an arboretum on the Eastern Highland Rim near Tullahoma, Tennessee were examined. The species were established in plantations of approximately one acre each, and varied in age from 5 to 17 years. Estimates of variation were desired to assess the dependability of the taxonomic characters and to indicate the amount of improvement attainable in future intra- and interspecific breeding programs. A secondary objective of the study was to determine the species with the best potential for planting in Tennessee. The taxonomic features of needle length, number of needles per fascicle, number and position of resin canals, and percent composition of cortical monoterpenes were analyzed for 23 species. Growth characters investigated included survival, stem height and volume growth. Additionally, wood specific gravity and extractive content were determined for the 17 species having mean diameters in excess of 3 inches. Results of the taxonomic analysis verified the identity of the species and generally confirmed the accepted taxonomic grouping of pines. External morphological features displayed the most variation among species and were thus the most dependable as taxonomic characters. However, internal needle morphology and cortical monoterpenes provide additional characters when external morphological features are not sufficiently distinct, and can be most useful to those seeking to identify juvenile material. Species native to the Southeastern United States excelled in stem height and volume growth. On this basis loblolly, eastern white, and Virginia pine are recommended for timber production in Tennessee. Pond pine grew faster and produced more volume than any species except loblolly, and is highly recommended for further testing
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